Amago Motosato served as the seventh head of the Amago clan.  Motosato was the eldest son of Amago Toyohisa.

Upon request of the Mōri, Motosato became the adopted son of his grandfather, Amago Yoshihisa, became head of the clan, and served Mōri Terumoto.  Motosato received one of the characters in his name from Terumoto.  He did not have children with his wife, so he adopted his nephew, Shinji Magosanrō Nariyasu.  In 1596, he became head of the guard house for the Iwami Ginzan silver mine located in the Naka District of Iwami Province.  He adopted the name of Kuza Shōkan.  After the Battle of Sekigahara, the mine came under control of the Tokugawa clan, causing Motosato to move with the Mōri to Suō and Nagato provinces, and he died in Nagato Province in 1622.